Scientific Urban Legends

Galileo Galilei was the first to demonstrate that bodies of
different mass fall equal distances in equal times. He did this very
dramatically by
dropping a light and heavy ball from the Leaning Tower of Piza before an assembly
of students and skeptical faculty of the University of Pisa.
The balls reached the ground
at the same time, thereby proving Aristotle's physics wrong.

Galileo wasn't the first to do this. Flemish engineer/mathematician
Simon Stevin (1548-1620) did the experiment. Even earlier, the 7th
century Byzantine scholar John Philloponus (John the Grammarian) described the
experiment in detail, in language that leaves no doubt that he had
actually done it.

To make matters worse, Galileo probably didn't even do the experiment himself,
at least he never claimed he did. No document of the University of Pisa
mentions it, nor does any other independent source. The story was likely a fictional
invention of Vivani, Galileo's pupil and biographer.
Galileo did describe such an experiment, and used it when arguing
against Aristotelian mechanics. The myth still shows up in
textbooks. It should have died when Lane Cooper demolished it in a pahmphet
titled Aristotle, Galileo, and the Tower of Pisa (Ithica,
1935; Kennakat Press, 1972).

Michael Faraday is visited by a delegation of government dignitaries.
They are shown his electric motors and other demos. One person says
"This is all very interesting, but of what possible use are these toys?"
Faraday responds: "I cannot say what use they may be, but I can confidently
predict that one day you will be able to tax them."

This is often repeated in various forms.
Sometimes the questioner is said to be "a woman", sometimes
"William Gladstone, then Chancellor of the Exchequer", and sometimes
it's merely "The Prime Minister". Seldom is a date given, and when given,
there's no consistency from one version to another. The great differences
between versions of this fable should make one suspicious of its truth.
Such an incident would surely have been
reported in newspapers. But there's no documentation for it. See
The Urban Legends
Reference Page, Quotes. Also see the next item.

Benjamin Franklin observes the first balloon ascension in 1783
while he was Ambassador at the Court of France. Someone asks
"What possible use are balloons?" Franklin answers "What use is a newborn baby?"

Franklin did observe the first balloon ascension on Nov 21, 1783 staged by
the Montgolfier Brothers. Franklin may have said this,
though there's no specific documentation. It was a common
riposte of that time, and still is today. It's unlikely that it is an original
witicism of Franklin. Sometimes it's seen attributed to Thomas Edison, and
no doubt he would have used it, too. I've even seen it attributed to Michael
Faraday (see previous item). Why is it that lame platitudes are
considered more important when attributed to a famous person? You can bet
that if Franklin or Edison did use such a quip, they didn't say "As the great
Leonardo da Vinci said when asked the use of one of his inventions...".

Glass windowpanes in old houses are thicker at the bottom because
glass is a liquid that flows slowly under the action of gravity.

This multiply mistaken unfounded assertion has even crept into
textbooks and physics lectures. It is true that windowpanes in old houses have varying thickness due to the glass manufacturing process used. In some cases the windowmaker chose to install them thicker side down. But that practice was not universally used. When old buildings have window panes thicker at the bottom, it was probably custom or preference on the part of the builder. Many old buildings have panes where the thick sides are oriented in various ways.

The second myth is the misleading assertion that glass is a liquid that flows slowly. There's some validity to this, for glass does sometimes flow, but so slowly and so little that in the time since the old glass was made, you'd not get anywhere near this much thickness difference, or even a noticable difference.

If the assertions were true, the amount of thickness observed in houses of the 18th century should be, on average much less than that observed in buildings of the 15th century. But that is not the case.

The thickness variation is observed in glass made by a process in which a layer of glass is flattented by rotation of molten glass. The resulting thickness varies from center to rim of the wheel. When cut into pieces, each piece has a thicker edge. A professional window-maker might choose to orient the thick edges the same way, for esthetic reasons. Also, we have an intuitive feeling that a solid object is more stable if its heavy side is down.

Modern glass for windowpanes is made by floating molten glass on a liquid surface, which produces a very flat surface and very uniform thickness.

Some versions are more specific, claiming that a "famous aerodynamicist" was asked how bumblebees can fly with such small wings relative to their body weight. He did some back-of-the-envelope calculations, and concluded that their wings were too small, and, aerodynamically, they shouldn't be able to fly. This story is much quoted in various forms, with different details, but without any documentation of who made the calculation, and when. So one suspects it is an "urban legend".

This popped up on an internet discussion group back in 1999, with this interesting response.

Subject: FW: Bumblebee Flight
Date: Wed, 13 Oct 1999 12:47:46 -0700
A long time ago [1989] I wrote an article for the journal AMERICAN
SCIENTIST entitled: "The Flight of the Bumblebee and Related Myths of
Entomological Engineering" (Am. Sci., Vol. 77, pp. 164-8). In this I
gave what still appears to be a correct account of the "Didn't the
aerodynamicist prove that the bumblebee can't fly? [sarcastic ha ha]"
story. I too had tried to find the name of "The aerodynamicist" who
did this to us. After a long search I was told by a very reputable
source that he thought that individual (who was badly misrepresented
subsequently by the "press") was the Swiss gas dynamicist Jacob
Ackeret - a famous name in supersonic aerodynamics. It was about the
right vintage, so I wrote that in my article without naming Ackeret
explicitly. Follwoing publication, however, I got mail. Boy did I
get mail - including half a dozen Xerox copies of portions of the text
of the book Le Vol Des Insects (Hermann and Cle, Paris, 1934) by the
famous entomologist August Magnan. On page 8 of the introduction, one
finds:
"Tout d'abord pouss'e par ce qui fait en aviation, j'ai applique' aux
insectes les lois de la resistance del'air, et je suis arrive' avec
M. SAINTE-LAGUE a cette conclusion que leur vol es impossible."
Thus the culprit is finally named: Sainte-Lague, Magnan's lab
assistant who was apparently some sort of engineer.
Share and enjoy.
John McMasters
Technical fellow
The Boeing company
Seattle, Washington

Rough translation of the quote from Magnan: "In the beginning, being encouraged by one who is into aviation, I have applied to the insects the laws of resistance for air, and I reached, with Mr. Sainte-Lague, the conclusion that their flight is impossible." If any reader can supply a more accurate translation, please let me know.